Aims

Accordingly, the aims of this study will attempt to answer the following:

1. Is it possible to monitor health and training adaptations during space flight from earth?
2. Is heart rate mediated by the autonomic nervous system in a similar way during rest and exercise in microgravity and on earth?
3. Does a predominantly eccentric based exercise programme performed pre-flight and in flight help to attenuate the adverse affect of microgravity both on post-flight orthostatic intolerance and muscle fiber damage?
4. What is the accuracy of heart rate monitoring in predicting total energy expenditure in microgravity compared against double labeled water, which has been previously validated in space?

Methods

The study will take place in 3 parts, which will be discussed here accordingly (see appendix 1).

Phase 1: PRE-FLIGHT

The study will begin 2 months before the date of departure to allow for the doubly labeled water (DLW) to “washout” before the mission. Prior to consumption of the DLW dose, base-line urine and saliva samples will be collected following an overnight fast, as previously described by Lane et al. (1997). After this initial dose, urine and saliva samples will be collected every 5 hours. For the next 4-6 days, fasting urine samples will be collected every morning in clean, dry cups while saliva samples will be collected by placing a dried dental cotton roll in the mouth for two minutes. MS will be required to collect these samples at least 30 minutes after the consumption of any food or fluids (Lane et al., 1997). Body weight will also be measured at this time using a calibrated digital scale.

To determine the heart rate - energy expenditure relationship specific to MS, an individual calibration test using the Cosmed portable telemetric gas analyser will be performed 2 months before the mission, and again immediately prior to the flight. This test will follow approximately 2 hours after the ingestion of a typical breakfast. The heart rate - energy expenditure relationship will be determined by measuring heart rate, oxygen consumption (VO2) and carbon dioxide production (VCO2) simultaneously for 7 to 8 workloads of increasing intensity and each lasting 4 – 5 minutes. Energy expenditure (kJ) will be determined for each workload, using the equations of Weir (1949). Analyzer outputs will be processed by a personal computer, which will calculate breath-by-breath ventilation, oxygen consumption (VO2), rates of carbon dioxide production (VCO2) and respired exchange ratio (RER), using conventional equations. In the first 3 stages of the protocol, MS will be tested in the supine resting position, followed by sitting and subsequently standing. Following these resting measurements, he will perform 5 progressive stepping exercises, beginning at a step height of 30 cm, at 80 steps per minute, increasing to a step height of 50 cm at 100 steps per minute. Individual heart rate – energy expenditure calibration curves will then be calculated using a non - linear regression equation.

MS will then wear a heart rate monitor for 24 hours that will record heart rate every minute under free living conditions. The 24 - hr free living energy expenditure will then be determined using the minute-by-minute heart rate values and will predict energy expenditure from the individual heart rate – energy expenditure curves.

During this phase, MS will consume his normal diet and will also be provided with a digital balance, on which to measure his food and a diet log, on which he is to record all food consumed, including the method of preparation, the quantity, and time and date of the food consumption (Lane et al., 1997). Any exercise and drug usage will also be recorded in this log.

Approximately 4 weeks before the date of take off, MS will be asked to include specific exercises into his general training programme. These exercises will consist of both cardiovascular exercises and specific eccentric resistance type exercises. Exercise sessions will be scheduled to take place every second day at the convenience of MS. Pre-flight exercises will serve as a possible preventative mechanism for adverse post-flight cardiovascular and neuromuscular effects as well as helping to ensure that MS is familiarized with those exercises to be performed in-flight.

Each week pre-flight, MS will also be required to perform a standardized exercise test which consists of the stand test, described previously by Buckey et al. (1996a), followed by an interval exercise test (see appendix 2). The modified stand test aims to determine cardiovascular function during orthostatic stress. This test requires the subject to lie supine for 10 minutes (29 minutes in the original test, but has been modified in this study in the interests of time constraints) in order to gather resting measurements which will be followed by a 10 minute standing period. The subject will be required to relax his legs and not to contract them. The test is terminated at the end of 10 minutes or when the subject requests to sit down. The modified stand test will be performed before exercise and no earlier than 2 hours before meal. MS will be asked to refrain from both caffeine and alcohol 12 hours before the test. Heart rate will be measured continuously during both supine lying and standing, while blood pressure will be recorded after 5 and 9 minutes of supine lying, every minute during standing and again at the end of the test.

As soon as possible thereafter, MS will be asked to perform the cycling component of the test. This test requires MS to cycle on a stationary cycle ergometer and to maintain a set cadence that will be controlled by a metronome. The test will consist of 4 exercise sessions each separated by a 1-minute rest period. The exercise intensity of each exercise session will increase incrementally. The 4th exercise session will be followed by a 5 minute recovery period, during which time MS will be asked to keep as still as possible.

Measurements obtained from the combined tests include supine resting heart rate, blood pressure and heart rate variability; standing resting heart rate, blood pressure and heart rate variability; exercising heart rate, blood pressure and heart rate variability and recovery heart rate, blood pressure and heart rate variability. Heart rate variability will be measured during this time by means of a heart rate monitoring system and R-R intervals will be analyzed using a frequency domain method. Breathing frequency will be controlled during these tests by means of a metronome in order to exclude respiratory drive as a possible confounding variable. A rating of perceived exertion (RPE) will be obtained from MS during each test. Other variables measured before each exercise test will be body weight, muscle strength, mid-thigh girth circumference and lower limb flexibility.

Muscle strength will be measured using a portable strain gauge. MS will be asked to exert maximal force with the right quadriceps during which time maximal strength will be recorded. This measurement will be correlated to the mid-thigh girth, measured at the mid point between the sub-gluteal and above knee girth measurements. Hamstring flexibility, taken as an estimate of lower limb flexibility, will be measured using the straight leg raise technique. MS will be asked to lie supine and lift his right leg. The investigator will passively flex his leg until he reaches his maximal range of motion. This angle will be measured with a goniometer with 180° being the leg in full extension.

These tests will be performed once a week on the same day and at the same time of day for the 4 weeks before the flight.

One week before take off, MS will undergo a complete anthropometrical analysis for the determination of percentage body fat, lean thigh volume and lean muscle mass using the methods of Durnin and Womersley (1974), Ross and Marfell-Jones (1991) and Katch and Katch (1974) respectively. A 5ml venous blood sample will also be taken at this time for the analysis of blood cell volume, immune function and hormonal status.

An incremental bicycle ergometer test to exhaustion will then be performed to determine peak oxygen consumption. MS will begin cycling at a work rate corresponding to 2.2 times his starting body weight (kg). After 150 seconds (2.5 minutes), the work rate will be increased by 50 Watts and by 25 Watts thereafter for each subsequent 2.5 minute stage. MS will be asked to maintain a cadence rate of 60 revolutions per minute (RPM). Exhaustion will be defined when MS is unable to maintain this predetermined cycling cadence or when he requests to stop the test. Oxygen consumption will be measured continuously during the test and peak oxygen consumption will be defined as the highest amount of oxygen consumed over a 30 second period. Heart rate will also be measured continuously using a heart rate monitor.

During this week, MS will also be asked to perform a second energy expenditure calibration test. On the day of the launch, MS will consume a second DLW dose.

Phase 2: IN-FLIGHT

Where possible, MS will participate in on-board exercise consisting of both cardiovascular and resistance type exercise. During this exercise time, heart rate will be measured continuously using the on-board electrocardiograph equipment. This heart rate data, where possible, will then be transmitted via satellite to Body iQ for real time data analysis and interpretation. Heart rate variability will also be analyzed continuously using the frequency domain method during rest, exercise and recovery. Mid-thigh girth measurements will also be gathered during this time, as will ratings of perceived exertion. On a predetermined day, MS will be asked to perform the exercise test, which will include measurements of resting heart and blood pressure, exercising heart rate and blood pressure and recovery heart rate and blood pressure. Supine and standing measurements will be merged for this test, as it will be impossible to separate the 2 conditions.

MS will be asked to keep a logbook that will simultaneously integrate exercise, corresponding heart rate and ratings of perceived exertion for every day that he is in microgravity.

Urine and saliva samples will be collected four to seven hours after the second dose of doubly labeled water. For the next 6 days, saliva samples will be collected immediately after the daily sleep period. Urine will be collected on the last day of the flight. The urine sample will be packaged in double polyethylene bags with Ziploc mechanisms. These will be stored with the saliva samples at ambient temperature (Lane et al., 1997). On 2 separate days, MS will be asked to record heart rate for 24 hours. The data collected during this time will be downloaded regularly and stored for the later determination of total energy expenditure. Food provided in-flight will be prepackaged as individual servings, and coded by a specific bar code on the wrapping. While in flight, MS will be asked to record the bar code from each serving during the meal, any fluid consumed, as well as including the time and date of consumption. Following the meal, any left over food will be resealed into specified containers and transported back to Earth.

Phase 3: POST-FLIGHT

Post-flight tests will be performed at 0-4, 24, 72 and 120 hours after landing. Within 4 hours of landing, MS will be asked to perform a series of post-flight tests. The exercise test will again include both supine and standing conditions at rest. Should MS be unable to complete this test, due to orthostatic intolerance or any other physiological reason, the time taken before the test is terminated will be recorded. Heart rate, heart rate variability, blood pressure and RPE will all be measured during this test. A full anthropometrical assessment will then be conducted on MS to quantify any whole body changes that may have occurred. MS will also be asked to repeat the muscle strength test using the strain gauge and the flexibility test using the straight leg raise. A second blood sample will also be taken for the analysis of blood cell volume, immune function and hormonal status. This testing protocol will be repeated again 72 hours post-flight.

Twenty-four hours after landing, MS will be asked to repeat the stand test during which time heart rate, blood pressure and RPE will be recorded. Body weight, mid-thigh girth and flexibility will also be measured. MS will then be asked to rate his perception of muscle pain on a scale of 1-10. He will be asked to rate this pain both at rest and during a standard functional squat movement. This testing protocol will be repeated again 120 hours post-flight.

On return to Earth all urine and saliva samples will be removed from the shuttle within hours of landing and prepared for analysis. The dental cotton will be centrifuged to obtain the saliva while the urine will be filtered using charcoal, and frozen immediately at -20° C. Baseline (prior to DLW dosing) urine, 1 void/day (for 5 days) and the last urine collection will be used in the analysis (Lane et al. 1997).